Might not mix Type F and any other fluids as the friction modifiers which make each one what they are are not the same. Type F has a higher initial "bite" and then "the bite" tapers off until full lock-up of the frictions happens, which results in the firmer shift, whereas the Dexron family fluids have less "bite" (for a bit more slippage upon initial engaagement of the frictions, though not real slippage per se) for a smoother shift feel. With the ATF-family fluids being different to allow the advanced electronics in the newer Chrysler automatics to do their thing and not cook themselves.
Back when the UltraDrives came out, the orig fluid spec was Dexron III + the Chrysler additive, but that was later changed to the "ATF-family" Chrysler-spec fluids. Without the additive, it was alleged that the UDs would later fail from slippage the trans controller could not fix.
In one of the old bulletin boards on the Internet, the Chrysler board (run by Dr. David Zatz) noted that Dexron fluids are allegedly "used up" after about 40K miles (only place I'd read that) and that ATF+3 was a superior fluid for longevity and semi-syn to be compatible with the internal seals of the older TFs and such. Then ATF+4 arrived to supercede it. So, no question that ATF+4 is a great atf, but their MIGHT be some incompatibilities with some lip seals and such, in the long run. Now, as time has progressed, I suspect that almost all of the transmission parts vendors have evolved into full-syn-compatible seals and such, so that issue might not be operative any more . . . unless the rebuild kit is NOS?
BUT, if the builder prefers Type F atf and has configured the frictions that were used to be compatible with it AND it causes no issues with lip seals and such, then I feel that should be whas is used in the transmission. As popular as it was in the performance market back then, in non-Ford automatics, I heard nothing about it causing any issues when it replaced Dexron in GM or other automatic transmissions.
As far as the pan gaskets, I suspect that any rubberized-cork gasket (OEM-spec Chrysler, etc.) can work well IF you add a skin coat of high-heat black silicone sealer on all sides and edges of it, letting it cure overnight, before installation. Just a thin coat spread out with a protected finger tip. This seals the rubberized-cork and prevents the lighter parts of the fluid from wicking through the cork parts of the gasket over time. It's worked well for me on ALL engine and trans pan gaskets for decades. Then ensure that the trans oil pan is FLAT with no indents where the bolts go through it. Snug-down the bolts with no excessive torque.
If you might desire to "get fancy", you can get a battery-powered extracctor unit to suck the atf out through the filler pipe. Amazon, eBay, and possibly Home Depot have them to do similar for changing the engine oil in mowers and such. Not very expensive, last time I checked. Just need an empty container(s) to put the old oil into for recycling. This way, no need to drop the pan for a fluid change.
IF some higher-temp resistance might be needed, seems like there might be some synthetic Type F fluid available somewhere, just as there used to be synthetic Dexron III atf.
Just some thoughts,
CBODY67